Weight watching Reducing people's options for junk foods helps them to cut back on the amount of 'junk food' kilojoules they take in, but it doesn't reduce their overall intake, according to a US study.

"Limiting variety was helpful for reducing intake for that type of food group, but it appeared that compensation occurred in other parts of the diet," says study lead author Professor Hollie Raynor of the University of Tennessee.

The results of the study, which appeared in the American Journal of Clinical Nutrition, offer a cautionary note to dieters who may be limiting their food variety - such as by cutting out carbs - to be watchful of all kilojoules coming in, not just those from the targeted food group.

Previous studies have shown that people with less variety in their diets tend to be more successful in losing weight and keeping it off. Raynor says she wanted to see if restricting options for high-kilojoule, low-nutrition foods, such as ice cream, cookies and chips, could help people lose weight.

Raynor's team asked 200 overweight and obese adults to make lifestyle changes aimed at losing weight. These included taking part in group meetings that discussed healthy behaviour, eating a kilojoule-reduced diet and increasing physical activity.

Half of the people were also told to limit the junk food in their diet to just two options, with the idea that monotony in the menu leads to a lack of interest in the food.

Over the 18 months of the study, people in the limited junk food group ate fewer types of treats each day - two to three - than the other group, which ate about four. They also ate fewer daily kilojoules from junk food.

At six and 12 months into the study, the people in the low-variety group ate about 420 fewer junk food kilojoules each day than the other group. By the end of the study, they were eating 330 fewer junk food kilojoules each day.

Similar results

Both groups ate less total kilojoules over the course of the study, and lost weight. But the overall reduction in kilojoules and weight loss - around 4.5 kilograms - was the same in each group.

"It makes sense to try and reduce the amount of variety in the diet, but human beings enjoy eating, so they will find other food components to consume than the ones that are being limited," says Alexandra Johnstone, a researcher at the University of Aberdeen in Scotland, who was not involved in the research.

She adds that to make a limited variety diet work, it will be important to also limit the portion sizes.

Raynor says that the message to dieters is that if they are trying to lose weight by restricting the variety in their food choices, they should be aware of their other food choices so it doesn't undermine their efforts.